The study, published in The Journal of the American Medical Association, compares the self-reported weight of 841 pancreatic cancer patients and 754 healthy people studied at the University of Texas M.D. Anderson Cancer Center.

Participants recalled and reported their weight starting at age 14. Here are the key findings:

People who had been overweight from age 14-39 were 67% more likely to be pancreatic cancer patients.

People who were obese from age 20-49 were about 2.5 times more likely to be pancreatic cancer patients.

Pancreatic cancer began two to six years earlier in people who were overweight or obese from age 20-49.

Among pancreatic cancer patients, people who were overweight or obese in the year before their pancreatic cancer diagnosis had a worse survival rate, regardless of the stage of their tumor or whether they had surgery to remove their tumor.

Youth a Key Time

Obesity had already been linked to greater risk of pancreatic cancer. But the new study shows that the teen and young adult years are "the critical period that has the strongest risk association," researcher Donghui Li, PhD, tells WebMD.

The age-related findings were also striking to Len Lichtenfeld, MD, deputy chief medical officer at the American Cancer Society and Gagandeep Singh, MD, FACS, director of the Liver and Pancreas Center at the John Wayne Cancer Institute in Santa Monica, Calif.

"I think the most important thing here, the take-home message, is it's important to be healthy and fit when you're younger," Singh tells WebMD. "Not that you can let go as you're older, but I think that the more obese you are at a younger age, the more problems with cancer you're likely to have."

"If we're going to tackle the problem of overweight and obesity in general, we really need to start with our children," says Lichtenfeld, who stresses the importance of eating a healthy diet rich in fruits and vegetables, getting regular exercise, and maintaining a healthy weight throughout life.

The study doesn't prove that extra weight causes pancreatic cancer. But when Li and colleagues considered other factors, such as diabetes and smoking, the results held.

Li, who is a professor in the department of gastrointestinal medical oncology at the University of Texas M.D. Anderson Cancer Center, cautions that the findings need to be confirmed.

"There are a lot of people who are overweight. Not everyone gets cancer," Li says. "There have to be some other factors that modify the association between obesity and the cancer -- for example, there may be genetic factors, dietary factors, and other risk factors associated with pancreatic cancer." Li's team is looking into that.

Pancreatic cancer, which often isn't found in its early stages, has a poor survival rate, and research on the biological basis of its connection to extra weight may yield much-needed clues for prevention and treatment, states an editorial published with the study.